I have been using Arch for a half a decade at this point and its worked out well for me. I like how its very stable despite being bleeding edge (relatively speaking). It’s made gaming a lot easier, and I was pleasantly surprised when Valve announced SteamOS was switching to it as a base.

A lot of people have varying levels of purism when it comes to linux, and it sounds like your friend dipped his toes in with Arch and realized “not pure enough” and then jumped in on the deep end with Gentoo. At the end of the day, Linux is Linux no matter which distro you pick, but each distro highlights different strengths and weaknesses of it. Its all about the package managers, the repository contents, and the maintainers. Occasionally, technical support might matter.

So, pick whichever distro you like, move around a bit to see what has the least papercuts for you, and then stick with that until you can’t anymore.